1. Field of the Invention
The present invention relates to an attachment device for panes, particularly panes of glass, comprising retainers arranged between each pane of glass and a support structure with a view to transferring the loads from panes to the support structure, which retainers comprise means for compensating for the dimensional variations or differences, deformations and displacements between the pane and the support structure.
2. Discussion of the Background
In the glass-construction industry, there are, in general, many known elements for retaining or attaching at isolated points which support glazing, for example in a facade cladding, only over a small area. They make it possible to produce largely transparent constructions requiring little in the way of optical materials.
There are in existence systems which support glazing in pairs at its edge and which pass through the joins between panes. Other retainers pass through holes made in the glazing.
Various loadings assume importance in glass constructions for reasons of safety. On the one hand, there are the external loadings (the weight of the glass itself, wind, precipitation, shocks, etc.). On the other hand, there are stresses exerted by constraints (impeded or prevented deformations, or compensation movements, resulting from temperature variations, tolerances in the support structure and fitting errors, for example). It is known that glass is extremely fragile and, unlike ductile materials (metals or plastics for example) can tolerate only extremely small amounts of elastic deformation and no plastic deformation at all.
In theory, the glass therefore must experience minimum mechanical stressing when loads exerted on it are transferred to the support structure of framework.
The matter of determining which of the effects described themselves produce stresses in the glass depends on the static system, that is to say, in particular, on the way in which the panes of glass are mounted.
Unfavourable static systems demand greater thicknesses of glass with a higher self-weight and therefore a stronger support structure. If the mounting is statically indeterminate then the panes will experience stresses both from the external loading and from pressures. By contrast, if the panes are mounted in a statically determinate manner, only the external loadings will be exerted, whereas the pressure loadings will be compensated for in the system or will even not occur. The tensions in the glass resulting from the external loadings are also lower when the mounting is statically determinate than when the panes are more firmly attached.
Known retaining systems using isolated points already make it possible to fulfill these requirements satisfactorily. Spherical or ball joints permit torsion between the glass and the support structure. However, the isolated point supports with spherical joints do not yet in themselves constitute a truly statically determinate manner of mounting a pane of glass. This result can be achieved only by means of additional freedoms in translation.
There are also in existence retainers at isolated points with spherical and sliding joints. In a retainer disclosed by document DE-44 00 979 C2, a lower spherical bushing is attached to the support structure. Its normal axis is perpendicular to the surface of the pane of glass that is to be attached. A compensation piece is placed on this spherical bushing so that it can pivot like a sphere, but without there being any degree of freedom in translation with respect to the normal axis. A support piece is held on the compensation piece in such a way that it can move perpendicularly to the said normal axis, that is to say parallel to the pane of glass that is to be attached, in all directions within a limited field. However, its adjustable and almost clearance-free axial guidance allows pivoting movements only with interaction with the compensation piece. On the support piece, the pane of glass is clamped onto a thin elastic insert using a screw which passes through a hole in the surface of the glass.
Document DE-43 40 511 A1 describes a stress-free attachment device for panes of glass, in which device each retainer comprises a universal joint on the pane side, in some embodiments with a free bearing, a hinge joint arranged spatially some distances from the universal joint is provided on the support structure side. It may be replaced by a slideway for compensating for tension by sliding, the practical configuration of which slideway is not, however, described in greater depth.
Document DE-44 45 724 A1 describes an attachment device for panes, the retainers of which have a universal joint essentially on one side. Some axial direction from this joint, depending on the embodiment, there may be another spherical joint or hinge joint. The particular features relating to compensation for stresses by translation or sliding are not disclosed.
The invention now intends to produce an attachment device of the type described in the introduction, advantageously without a universal joint, in which, degrees of freedom in rotation in compensation means of the retainers are embodied solely by uni-axis pivoting joints.
According to these advantageous developments, the retainers further comprise compensation means with degrees of freedom in translation so as to allow relative displacements, at least over limited distances, between the pane and the support structure, these displacements being due, for example, to thermal expansion.
According to one development of the invention, uni-axis hinge joints may be produced in a particularly simple way so as to allow sliding which in itself is restricted in the direction of the axis of the hinge. Such an embodiment, if need be, then allows the pivoting and sliding movements to be transferred locally or strung together. Hinge joints can be produced in the form of bushes and pins or from pairing two cylindrical surfaces, one convex and one concave, with one another for sliding, there being appropriate safeguards against lifting included.
A retainer in the form of a free bearing preferably comprises two hinge pins which extend at right angles to each other in projection. In this instance they may form an intersection or may lie some distance from one another.
It is also possible to separate the two degrees of freedomxe2x80x94xe2x80x9cpivotingxe2x80x9d and xe2x80x9cslidingxe2x80x9dxe2x80x94in the spatial and functional plane, for example by arranging the base of one hinge on a support so that it can be displaced flat or along an axis on a support.
In another advantageous embodiment, a retainer may also have a degree of freedom in rotation with respect to its longitudinal axis intersecting the pane.